Page 112 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Use double GI strip size 30mm x 10mm to connect GI plate to system earthing.
It will be better to use GI pipe of size 2.5’ diameter with flange on the top of GI pipe to cover GI strip from earth
plate to top flange.

Cover top of GI pipe with a T joint to avoid jamming of pipe with dust and mud also use water time to time through
this pipe to bottom of earth plate.
Methods of reducing resistance of earth electrode

1 Pouring water in the earth pit at repeated intervals lowers the earth electrode resistance
2 After installing the rod or pipe or plate in earth, the earth pit should be treated with layers of coke and common
salt to get a lower value of earth resistance

3 Connecting a number of earth electrodes in parallel reduces the earth electrode resistance
4 Soldering the earth connections or using non –ferrous clamps lowers the electrode resistance
5 Avoiding rust in the earth electrode connections lowers the earth electrode res
Purpose of double earthing
1 Doubleearthing shall be provided for all electrical machines.
2 Doubleearthing is provided to machines to ensure earth continuity even if one of the earth continuity conductor
is opened or damaged.
3 Doubleearthing is also reduce the resistance of earth continuity conductor.

Application
Use of plate electrode is recommended only where current carrying capacity is the prime consideration. For
example:
Telecommunication, Transmission, Substations and power generations, Transformers and neutral earthing,
Lightning arrestor earthing, Equipment body earthing, Water treatment plants, Heavy industries, College,
Hospitals, Banks, Residential building.
Earthing-ie rules &iee regulations
• Earth pin of 3 pin lighting plug & 4 pin power plug socket should be efficiently earthed

• All metallic covering of electric supply line such as iron clad switches & iron clad DBs, GI pipes enclosing
cables, down rod of fan should be earthed

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CITS : Power - Electrician & Wireman - Lesson 20-25 CITS : Power - Electrician & Wireman - Lesson 20-25